ATR-FT/IR Study on the Interactions between Gliadins and Dextrin and Their Effects on Protein Secondary Structure

Abstract

The effects of heat treatment and dextrin addition on the secondary structure of gliadins were investigated by means of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT/IR). Gliadins and gliadin/dextrin mixtures (before and after thermal treatment) were prepared as a dried protein film on the ATR-FT/IR zinc selenide cell plate and equilibrated at a water activity (a(w)) of 0.06. The results show that gliadins undergo conformational changes upon thermal treatment both in the absence and in the presence of dextrin. In particular, in the thermally treated gliadins, the decrease of the band at around 1651 cm(-)(1) and the increase of the bands at around 1628 and 1690 cm(-)(1) suggest a loss of alpha-helix structure and a higher content of protein aggregates. The same trend was observed in the presence of dextrin. Concerning the interactions between gliadins and dextrin, gliadin/dextrin mixtures show variations in the amide I region compared to native gliadins (e.g., an increase of the band at 1645 cm(-)(1) and the absence of the band at around 1668 cm(-)(1)) that might be due to hydrogen bond formation between gliadins and dextrin. It was also found that the spectrum of gliadin/dextrin mixtures was less affected by the hydration state than that of native gliadins, as observed from the differential spectra obtained by subtraction of the spectrum obtained at a(w) = 0.06 (driest condition tested) from the spectrum of the sample equilibrated at a(w) = 0.84. This could be due to the fact that C=O and N-H groups of gliadins are engaged to form hydrogen bonds with the hydroxyl groups of dextrin, and so they are not perturbed by the presence of water molecules. Finally, water activity effects on the secondary structure of gliadins are also discussed.

Relationship between digestibility and secondary structure of raw and thermally treated legume proteins: a Fourier transform infrared (FT-IR) spectroscopic study

“…A band at 1,690 cm -1 has been observed in the FSD spectrum of red bean globulin and lentil lectin (Chehin et al 1999;Meng and Ma 2001). Moreover, high frequency contributions around 1,690 cm -1 have been found to increase in gliadins subjected to heat treatments and unambiguously associated to intermolecular protein aggregation (Secundo and Guerrieri 2005). The presence of a low-frequency band at 1,610-1,620 cm -1 has been addressed as a marker for intermolecolar protein complexes (Murayama and Tomida 2004;Carbonaro et al 2008).…”

“…Moreover, a component around 1,682 cm -1 assigned to a high wavenumber antiparallel b-sheet Fig. 2 The amide I band and its spectral deconvolution with Gaussian contribution of common bean, chickpea and lentil contribution, has been detected in several plant food proteins, including wheat gliadins, red bean globulins and lentil lectin (Chehin et al 1999;Meng and Ma 2001;Secundo and Guerrieri 2005). Thus, we assume that the bands centred in the ranges 1,660-1,670 cm -1 and 1,670-1,680 cm -1 are due to turns' conformations (T1 and T2 bands, respectively), while those between 1,680-1,688 cm -1 originate from antiparallel b-sheet structures (b -A).…”

“…Thus, FT-IR appears particularly suitable in controlling functional properties of food proteins during technological processes. FT-IR spectroscopy has been successfully applied to monitor structure of isolated soy, buckwheat, oat globulins and wheat gliadins under the effect of pH, salts, and thermal treatments (Choi and Ma 2005;Secundo and Guerrieri 2005). In addition, structural modifications underlying development of hard-to-cook phenomenon in common beans, have been explored by FT-IR analysis of extracted protein fractions (Maurer et al 2004).…”

Interaction of α‐gliadin with polyanions: Design considerations for sequestrants used in supportive treatment of celiac disease

“…Gliadin contains a nonrepetitive domain rich in ahelical structure and a heterogeneous repetitive domain rich in b-reverse turns. 14 Figure 2 shows far-UV CD spectra of agliadin as a function of the concentration of PSS (A), PHS1 (B), and PHS2 (C), measured at pH 1.2, and at a protein concentration of 150 mg/L. The spectra were collected until a polymer concentration giving a high voltage of up to 600 V at wavelengths below 222 nm was reached.…”

Development of active bioplastics based on wheat proteins and natural antimicrobials for food packaging applications

“…region is ascribed to N-H stretching vibrations and the group of bands in the 3000-2800 cm -1 region corresponds to the characteristic C-H vibrations (Secundo and Guerrieri, 2005).…”